We characterize two-dimensional (2D) microtubule-based active nematics driven by light-responsive kinesin motor clusters. We assess two constructs of optogenetic kinesin: opto-K401, a processive motor, and opto-K365, a non-processive motor. Measurements reveal an order of magnitude improvement in the contrast of nematic flow speeds between maximally- and minimally-illuminated states for opto-K365 motors. Focusing on opto-K365 nematics, we characterize both the steady-state flow and defect density as a function of applied light and examine the transient behavior between steady-states. The steady-state nematic flow and defect densities are set by the applied light intensity across centimeter-sized samples, independent of initial conditions. Although nematic flow reaches steady-state within tens of seconds, the defect density exhibits transient behavior for 4 to 10 minutes, showing a separation between small-scale active reorganization and system-scale structural states. This work establishes an experimental platform to test theoretical frameworks which exploit spatiotemporally-heterogeneous patterns of activity to generate targeted dynamical states.
@article{arxiv.2303.02945,
title = {Light-activated microtubule-based 2D active nematic},
author = {Zahra Zarei and John Berezney and Alexander Hensley and Linnea Lemma and Nesrin Senbil and Zvonimir Dogic and Seth Fraden},
journal= {arXiv preprint arXiv:2303.02945},
year = {2023}
}